1. Field of the Invention
The present invention relates to a belt type stepless shifter for vehicles comprising a pair of pulleys with the effective diameter variable and a driving V-belt between these pulleys, and more particularly to an improved stepless shifter which can increase the amount of transmitted torque.
2. Description of the Prior Art
A belt type stepless shifter is known which comprises pulleys mounted on input and output shafts disposed in parallel, each of an said pulleys including a movable flange axially driven by hydraulic servo means composed of annular cylinder and piston, disposed on the concentric axis to the shaft, and a stationary flange in opposition to the movable flange so as to constitute a V-shaped space for a V-belt between opposite surfaces of both flanges, and a V-belt connecting these pulleys, thereby regulating the revolution radius of the V-belt is regulated by supplying or exhausting of oil in the annular cylinder. In order to increase the amount of torque transmitted between the input and output shafts in such a belt type stepless shifter and to prevent slippage of the belt, hydraulic pressure supplied to the annular oil chamber of pulleys must be increased, or the pressure carrying area of the movable cylinder or piston connected to the movable flange must be increased. In general, increase of the hydraulic pressure requires increase of the driving power of the oil pump, and increase of the pressure carrying area requires increase of the outer diameter of the shifter.